Delays upset traders (7)
I believe the answer is:
retards
'delays' is the definition.
(I know this)
'upset traders' is the wordplay.
'upset' is an anagram indicator.
'traders' with letters rearranged gives 'RETARDS'.
(Other definitions for retards that I've seen before include "Slows the growth of" , "decelerates" , "Delays, slows the progress of" , "Holds back, slows down." .)